Process for refining lead-bismuth alloys



Jan. 5, 1932. J. .1. FINGLAND ET AL PROCESS FOR REFINING'LEAD BISMUTH ALLOYS Filed May 9, 1929 Patented Jan. 5, 1932 UNETED STATES PATENT GFFICE JCHN .IAMEs FINGLAND, ALEXANDER DOUGLAS TURNBULL, AND PETER FINDLAY MCINTYNE, or TRAIL, BRITISH COLUMBIA, CANADA, AssIGNcRs To THE CoNso-LI- DATED MINING AND sMELTINCr COMPANY oF CANADA, LIMITED, on MONTREAL, aUnBEc, CANADA, A CCMPANY or CANADA PROCESS FOR REFINING LEAD-IBISMUTH ALLOYS .Application led May 9, 1929. Serial No. 361,834.

Our invention relates to a process of refining lead-bismuth alloy, containing 40% bismuth, which comprises` heating a charge of the crude alloy to a temperature above its fusing point, adding zinc to the molten charge, agitating it at that temperature, slowly cooling it, by successive stages, progressively graduated from the maximum temperature of the charge to the freezing point of the residual lead-bismuth alloy, and removing at each stage, the solidifying metals and impurities, for the production at the nalstage of a low freezing lead-bismuth alloy, substantially free from the other'metals and impurities with which it was associated at the initial stage of the operation.

The refining of the alloy may be conducted by effecting the heating and the subsequent succession of coolings in a single receptacle but it is more practical to conduct them separately in a plurality of heated receptacles arranged in differential thermal-series definitely graduated between the maximum and minimum temperatures of the operation, and transfer the solidifying metals and impurities, in the form of crusts, from the cooler to the hotter receptacles yand the liquid metal from the hotter'to the cooler receptacles, until a residual liquid lead-bismuth valloy is obtained in the last receptacle of the series free or substantially free from other metals and impurities, including the zinc, added to the charge at the initial stage of the operation.

A suitable plant for carrying out the process, shown diagrammatically in the accompanying drawing, may consist of a battery of six 5-ton kettles, at one end of which is a irebox for providing the necessary heat with provision for conducting the gaseous products of combustion around each kettle in succession and thevnceto the stack; the heating arrangements being sufficient to maintain A 1100o F. in the first kettle and 400 F. in

the last kettle of the series, and the actual procedure being carriedvout as follows A charge of crude lead-bismuth alloy is heated to a temperature of about 1000 F. in the second kettle and from 11/2 to 3% zinc is added t'o the molten chargewhich is i agitated with a mechanical stirrer at that temperature. The successive crusts of the second kettle are transferred to and accumulated in the first kettle until it contains a full charge from a number of like operations.

The charge in the first kettle, is re-melted and stirred at a temperature of about 11009 F.

and the crusts are removed from it and sepaf rately treated by known metallurgical methmoved from it, is transferred to the third kettle heated to a temperature ranging between 800", and 900 F. As cooling proceeds the crust is transferred from the third kettle to the second kettle for retreatment with a subsequent charge in the second kettle, and the liquid metal in the third kettle is transferred to the fourth kettle heated t0 a temperature ranging from 600 to 7 00 F.

The crustyof the fourth kettle is transferred to the third kettle and the liquid metal in the fourth kettle is transferred to the fifth kettle heated to a temperature ranging between 3000' and 500 F, The crust of the fifth kettle is transferred to the fourth kettle and the liquid metal in the. fth kettle is transferred to the sixth kettle to give a low freezing liquid lead-bismuth alloy free or substantially free from other metals and impurities. The application of this procedure finally resolves the original charge' into two products; one of which consists of lead-bismuth alloy, freel or substantially free from impuritiesand from other metals such as gold, silver, arsenic, antimony, and added zinc, suitable for the recovery of bismuth by electrolytic or other metallurgical operations; and another which consists chiefiy of` the other metals contained in the crude charge such as gold, silver, arsenic and antimony together with the added zinc and small proportions of lead and bismuth, to be treated by known metallurgical methods for the recovery of the valuable contents.

The following example indicates the com'- of arsenic and 0.25% antimony, together with the addition of 21/2% zinc.

Sil- Gold ver- Temp. ozs. per om per Zinc F' ton ton Orusts kettle:

#2 passing to kettle #l 4. 12 1786. 6 20.0 1100-900 *3 passing to kettle #2 0. 54 969.6 16.0 900-800 pusing to kettle #3 0. 03 817. 4 15.3 700-600 5 pass ng to kettle #4 Trace. 115. 0 8. 6 50o-300 Liquids ke ..tle:

passmg to kettle #3 0. 03 235. 5 6. 0 pass ng to kettle #i 0.01 93. 6 3.7 #4 passing to kettle #5 Trace. 14. 1 1, 5 #5 passing to kettle #6 Trace Trace. Nil.

Having thus fully described our invention what we claim `as new and desire to secure by Letters Patent is:

1. A process of refining lead-bismuth alloy containing 20-40% bismuth, which comprises incorporating zinc with a charge of the crude alloy in a fusing vessel, heating it, maintaining the heat at an uniform temperature throughout the charge materially above its fusion point, transferring the crust of the molten charge to a separate vessel uniformly heated to a higher temperature than said fusing vessel and the liquid residue of the charge to a succession of separate vessels, the temperatures of which are progressively graduated from the maximum of the graduated temperatures tothe freezing point of the residual lead-bismuth alloy, maintaining each vessel at an uniform temperature throughout the charge, transferring the solidifylng metals and impurities from each of the lower heated vessels to the next higher heated vessel in succession and transferring the liquid residue from each of the higher heated vessels to the next lower heated vessel in succession for the production, atthe lowest heated vessel, of a low freezing lead-bismuth alloy substantially free from the other metals and impurities with which it was associated at the commencement of the operation.

2. A process of refining lead-bismuth alloy containlng 20-4070 bismuth, which comprises incorporating zinc with a charge of the crude alloy in a fusing vessel, heating it and maintaining the heat at a substantially uniform `temperature of 1000" F. throughout the charge, transferring the crust of the molten charge to a separate vessel uniformly heated to a temperature of substantially l1 00 F. and the li uid residue of the charge to a succession o separate vessels the temperatures of which are progressively graduated from 900 F. to 300 F., maintaining each vessel at an uniform temperature throughout the charge, transferring the solidifymg metals and impurities from each of the lower heated vessels to the next higher heated vessel in succession and transferring the liquid residue from each of the higher heated vessels to the next lower heated vessel in succession for the production, at the lowest heated vessel, of a low freezing lead-bismuth alloy substantially free from the other metals and impurities with which it was associated at the commencement of the operation.

3. A process of refining lead-bismuth alloy containing 20-40% bismuth, which comprises incorporating from one and one half per cent to three per cent of zinc with a charge of the crude alloy in a fusing vessel, heating it, maintaining the heat at an uniform temperature throughout the charge materially above its fusion point, transferring the crust of the molten charge to a separate vessel uniformly heated to a higher temperature than said fusing vessel and the liquid residue of the charge to a succession of separate vessels, the temperatures of'which are progressively graduated from the maximum of the graduated temperatures to the freezing point of the residual lead-bismuth alloy, maintaining each vessel at an uniform temperature throughout the charge, transferring the solidifying metals and impurities from each of the lower heated vessels to the next higher heated vessel in succession and transferring the liquid residue from each of the higher heated vessels to the next lower heated vessel in succession for the production, at the lowest heated vessel, of a low freezing leadbismuth alloy substantially free from the other metals and impurities with which it was associated at the commencement of the operation.

4. A process of refining lead-bismuth alloy containing 20-400/0 bismuth, which comprises incorporating from one and one half per cent to three per cent of zinc with a charge 4of the crude alloy in a fusing vessel, heating it and'maintaining the heat at a substantiallyv uniform temperature of 11000o F. throughout the charge, transferring the crust of the molten charge to a separate vessel uniformly heated to a teinperature of substantially 1100o F and the liquid residue of the charge to a succession of separate vessels the temperatures of which are progressively graduated from 900 F. to 300 F., maintaining each vessel at an uniformtemperature throughout the charge, transferring the solidifying metals and impurities from each of the lower heated vessels tothe next higher heated vessel in succession and transferring the liquid residue from each of the higher heated vessels to the next lower heated vessel in succession forthe production, at the lowest heated vessel, of a low freezing lead-bismuth alloy substantially free from the other lli metals and impurities with which it was associated at the commencement of the operation.

5. A process of refining lead bismuth alloy containing 2040% bismuth by passing the charge through a series of separate thermal stages; which comprises incorporating zinc in a charge of the crude alloy; heating the charge at the initial stage to a temperature ranging between 900 F. and 1100 F.; removing the solidifying metals and impurities fromthe molten charge at the initial stage and transferring them to the crust melting stage and there heatingl them t0 a higher temperature than that of the initial stage; removing the liquid residue from the initial stage and passing it through a succession of separate` thermal stages of progressively descending temperatures graduated from 900 F. to 300 F.; maintainin an uniform temperature throughout the c arge at each stage; removing the solidifying metals and impuritiesat each stage and transferring them to the next higher heated stage of the series for the recovery of all the contained metals except the lead and bismuth; and removing the liquid residue at each stage and transferring it to the next lower heated stage of the series for the production at the lowest thermal stage of a low freezing lead bismuth alloy substantially free from the other metals and impurities with which it was associated at the commencement of the operation. y

6. A process of refining lead bismuth allo)7 containing 20-4070 bismuth which comprises incorporating zinc in a charge of the crude alloy, passing the charge through a series of separate thermal stages of progressively descending temperatures graduated from 1100 F. to 300 F.; maintaining at each stage an uniform temperature throughout the charge, passing the solidifying metals and impurities from each stage to the next higher stage of the series and the residual liquid from each stage to the next lower stage of the series and recovering, at the final st age at one end of the operation, a low freezing lead bismuth alloy substantially free from the other metals and impurities with which it was associated at the commencement of the operation, and at the nal stage at the other end of the operation a crust containing said other metals and impurities.

Signed at the city of Trail, Province of British Columbia, this 31st day of March,

JOHN JAMES FINGLAND.

PETER FINDLAY MclNTYRE. ALEXANDER DOUGLAS TURNBULL. 

